1. Field of the Invention
The subject invention generally pertains to HVAC systems and more specifically to an air conditioning system that includes a dehumidifying desiccant wheel.
2. Description of Related Art
Energy wheels and desiccant wheels are two distinct types of wheels used in the HVAC industry. An energy wheel is a rotating, porous mass that functions as heat exchanger by transferring sensible heat from one air stream to another. With an energy wheel, half the wheel absorbs heat while the other half releases it. Examples of energy wheels are disclosed in U.S. Pat. Nos. 6,141,979 and 4,825,936.
Desiccant wheels, on the other hand, transfer moisture from one air stream to another, usually for the purpose of reducing humidity of a comfort zone. Examples of systems with desiccant wheels are disclosed in U.S. Pat. Nos. 6,311,511; 6,237,354; 5,887,784; 5,816,065; 5,732,562; 5,579,647; 5,551,245; 5,517,828 and 4,719,761.
Although many air conditioning systems that are enhanced with desiccant wheels have been developed, such systems often implement the use of desiccant wheels whenever there is a dehumidification load. However many air conditioning systems may be most efficient if the desiccant wheel is only utilized at part load conditions or when the load on the system shifts from a sensible cooling load to more of a latent cooling or dehumidification load. Current systems often fail to address these efficiency concerns. Moreover, current systems with desiccant wheels often disregard a critical period when the refrigerant system is first activated. At startup, it takes a moment for the refrigerant system's evaporator to become sufficiently cold to remove moisture from the air. So, when the refrigerant system is first energized and before the evaporator becomes cold, condensed water on the surface of the evaporator may actually evaporate into the air, which can increase the humidity of the comfort zone.
Consequently, a need exists for air conditioning systems that are enhanced with desiccant wheels that address efficiency concerns at part load operation for variable air volume systems.